Conventionally, when a groove of a tire surface is excessively abraded, not only a legal problem has occurred but also running safety has greatly been affected. When managing such tire wear, a driver or a running manager visually checks a groove depth of a tread pattern or an appearance of a wear bar attached to the tire to inspect a worn state of the tire, and replaces the tire with a new tire when the tread has reached a worn state.
To bring this wear bar into clear view, a technology of coloring the wear bar or burying studs to generate abnormal noises has been disclosed (e.g., publication of unexamined utility model application No. 56-120901).
In the case of visually checking the worn state of the tire, when the driver or the like neglects inspection or takes a wrong checking method, it is not preferable because the tire is left as it is even if it reaches its wear limit. Thus, a technology has been disclosed, which detects tire wear by burying an optical reflection member having an optical reflection surface in a tread, the optical reflection surface reflecting a light applied from the outside when the tire is worn, and receiving the light (e.g., publication of unexamined application No. 11-170819).
However, according to the conventional technology described in the Patent Document 1, a tire appearance is damaged and, if anything, because of the buried studs, there is the danger that a road surface will be damaged when the tire is worn, or a damage of the tire will be quickened.
According to the conventional technology described in the Patent Document 2, as the reflected light is detected to check a worn level, when the reflection surface or the light reception surface is stained, the reflected light is not detected even if the reflection surface is exposed. Thus, it may not be recognized even when the tire reaches its wear limit.
Therefore, with the aforementioned problems in mind, it is an object of the present invention to provide a highly reliable tire wear detection system capable of detecting tire wear without damaging a tire or a road surface, and a pneumatic tire.